AmigaOne XE, manual cites incorrect vCore??

Hi, still have a broken cpuboard with spare 7457 which VCore requirement is too low (1.1)


I have measured the voltage of my unpopulated G4/745X board using pin A22 as ground and VDD (VCore) pins J9 and J11, both gave the same results.

http://www.nxp.com/assets/documents/d ... data-sheets/MPC7457EC.pdf

Pinout for 7457 begins at the end of page 40.



And it seems that each VCore jumper setting in the official Amigaone manual is off by one, they are actually for the VCore value setting that is listed above it.

http://intuitionbase.com/a1_xe.pdf (last two pages)


"ON OFF ON OFF" jumper short, which is meant for 1.59, is actually 1.54!

"OFF OFF ON ON" Jumper short, meant for 1.94, is actually 1.89

"OFF OFF OFF OFF" jumper short, meant for 1.34, is actually 1.29

"OFF OFF OFF OFF" jumper open, meant for 1.244, is thankfully for me, 1.20 volt (rounded as 1.2?)


Is this suppose to be like this ??


I haven't tested every setting, it is a bit time consuming as the solder pads are too close together, but if every setting is off by one then I think that these are the real VCore settings for the shorted jumper, with 1.2 at the bottom for convenience.

https://s7.postimg.org/ye530f72z/Amiga_One_VCore_short.jpg


I will be contacting NXP what my 7457's maximum VCore settings are, with the discovery of the 1.2 volt setting I am thinking about running my 7457 with a higher clock speed to be able to cope with it.



Could anyone point Criscot towards this? he seems to have a lot of experience with the XE and he might be able to explain it.
I think that he has a Facebook or Twitter account, I don't have one myself.

@Helloworld

Hello

I don't have the clues to work on this:I only know that in my humble opinion you must stay calm,take a rest and when you can do it again pùt in pravtice

Anyway good-luck and stay clear.

My goddess desire from years ago was that I could put at the max speed of 933 Mhz on my 750FX Amiga One.

Thank you and good luck!!!

i am running 7457 1.33 MHz on A1XEG4 no problems here if you want to compare vcore settings let me know

I suggest you measure the Vcore across one of the yellow capacitors. Every CPU model has its own preferred setting and there were several different types fitted to the SEs and XEs.

IIRC you are right about the table entries being "one off". I found the same thing.

You might improve reliability by adjusting the Vcore slightly, but be very careful of the toy heatsink. Unless you know what you are doing and can fit a better heatsink, I would leave well alone.

The reliability of the whole motherboard is limited by the Articia chip and the memory DIMM you have fitted. In my experience, every mobo is different and you have to match the memory DIMM to the mobo. Again, in my experience, trying to use two DIMMs is bound to fail. The Articia bus drivers just are not up to it.

Agreed care should be taken but the 7457 cpu is much more robust than its predecessor 7455. I am using 2 dimms without problems also.
But, and a big but, I did not get my MB modified at all. Just the upgrade to 7457 processor on the cpu module itself

I was using two DIMMs on a 7455 board (mismatched sizes, but I think they were both Infineon chips) without issue. I believe I increased the vCore slightly, but don't remember the details. I sold my A1XE a while back, so I can't check, but it was an "unfixed" board with the IDE on PCI rather than internal.

@tonyw

"trying to use two DIMMs is bound to fail. The Articia bus drivers just are not up to it."

False. I have 2 GB of ram in my XE G4 @ 1.26GHz ! (2x1 GB)

You simply all forgot that the XE was meant to be used SERVER Ram, not ordinary Desktop Ram :) (OK that ram is expensive, and was VERY expensive in 2002...)

but pour it with ECC fully buffered sticks and max it to 2 GB like me. your G4 will rewards you.

^^)

Typing this on my AmigaOne XE

;)